Conventionally, an electronic piano emits electronic sound from a loudspeaker in response to a player's depressing or releasing keys. Such electronic sound has been improved, and has recently reached some satisfactory level. However, the key touch of the electronic piano remains significantly different from that of an acoustic upright piano, despite various improvements.
Specifically, an action simulation mechanism has been developed for providing the electronic piano with a key touch similar to that of the acoustic upright piano. For example, Japanese laid-open Patent Application No. 4-347895 discloses the electronic piano, as shown in FIG. 11, incorporating a hammer arm P14 rotatable about a shaft P10 for depressing the rear end of a key P12, and, as shown in FIG. 12, incorporating a hammer arm P20 rotatable about a shaft P16 for pushing up the tip of a key P18.
The key touch of the acoustic upright piano is now generally explained. As shown in FIG. 14, when a player depresses a key 111, a wippen 115 rotates in the direction reverse to the rotary direction of key 111, or counterclockwise as viewed in FIG. 14. A jack 117 rotatably attached to the wippen 115, in turn, rises to push up a hammer butt 118, causing the hammer butt 118 to rotate in the direction reverse to the rotary direction of the key 111, or counterclockwise as viewed in FIG. 14, together with a hammer assembly 120 composed of a hammer shank 121, a hammer head 123 and a hammer felt 122. After the jack 117 rises to a predetermined position, placing a jack tail 117a in contact with a regulating button 116, the jack 117 leaves the hammer butt 118. Therefore, the hammer butt 118, the hammer shank 121 and the hammer head 123 are inertially rotated, thereby striking a string.
As aforementioned, in the acoustic upright piano, the wippen 115, the jack 117 and the hammer butt 118 are rotated on the different and respective rotary axes, and the jack 117 leaves the hammer butt 118 at a predetermined timing, providing the complicated touch of the key 111.
In the electronic keyboard provided with the action simulation mechanism as shown in FIGS. 11 and 12, however, the hammer arm and the key are rotated on a single axis, providing a monotonous or simple key touch, different from the acoustic piano.
In appearance, the electronic piano is compact. For example, the height of the frame roof of the electronic piano is slightly higher than the height of the keyboard. When the aforementioned action simulation mechanism is incorporated in the electronic piano, the height is increased. Therefore, it is difficult to attain the advantageous compact structure of the electronic piano.
Especially, as shown in FIG. 13, when the action simulation mechanism equivalent to the action mechanism of the acoustic piano is used, the aforementioned structural problem is remarkable.
The action simulation mechanism is composed of a wippen equivalent member 215, a jack equivalent member 217, a hammer equivalent member 221 and a stopper 232. The hammer equivalent member 221 includes a hammer butt, a hammer shank, a hammer head, a hammer felt, a catcher and a catcher shank. When a player depresses a key, the key is rotated, rotating the wippen equivalent member 215. When the wippen equivalent member 215 is thus rotated in response to the key depression, the jack equivalent member 217 is raised, pushing up the hammer equivalent member 221. The hammer equivalent member 221 is thus rotated, leaves the jack equivalent member 217, is further inertially rotated, and is placed in contact with the stopper 232, to stop. In this action simulation mechanism, unlike the action simulation mechanism shown in FIGS. 11 and 12, the wippen equivalent member 215, the jack equivalent member 217 and the hammer equivalent member 221 are rotated on the different and respective axes, and the jack equivalent member 217 leaves the hammer equivalent member 221 at a predetermined timing, providing a key touch which is similar to that of the acoustic upright piano. However, since the hammer equivalent member 221 has a substantial height, the height of the frame roof of the electronic piano is increased, and the compact appearance of the normal electronic piano cannot be maintained.